Fuel Containment System

ABSTRACT

A fuel containment system for an aircraft is provided. The fuel containment system comprises an upper fuel barrier under a cabin floor, an aft wheel well bulkhead, an aft fuel barrier opposite the aft wheel well bulkhead, a lower fuel barrier associated with a cargo floor, and a lower fuselage skin panel. A fuel tank is created by the upper fuel barrier, the aft wheel well bulkhead, the aft fuel barrier, the lower fuel barrier, and the lower fuselage skin. The fuel tank is integrated into the aircraft and existing structural components are sealed to prevent fuel from leaking out of the integrated fuel tank.

This application claims the benefit of U.S. Provisional PatentApplication Ser. No. 62/862,084, filed Jun. 16, 2019, and entitled “FuelContainment System.”

BACKGROUND INFORMATION 1. Field

The present disclosure relates generally to aircraft. More specifically,the present disclosure relates to a fuel containment system designed toincrease fuel capacity for an aircraft.

2. Background

Airlines are under constant pressure to more efficiently transportpassengers and cargo. One of the ways to make travel more efficient isto minimize stops between destinations. To do this, airlines need morerange out of their aircraft. Range is often determined by fuel capacity.Generally, the more fuel an aircraft can carry, the longer it can fly.Adding fuel not only makes flights more efficient but also opens thepossibility that an airline can serve new routes.

Installing auxiliary fuel tanks in an aircraft improves the fuelcapacity of that aircraft. These auxiliary fuel tanks store fuel that isthen pumped into a main fuel tank to power aircraft engines. Auxiliaryfuel tanks may be installed in compartments within the fuselage of theaircraft. They may be retro-fitted and removable. For example, anauxiliary fuel tank may be added to the cargo area to replace a cargocontainer or bulk cargo.

While adding fuel capacity extends aircraft range, the auxiliary fuelsystem increases the weight of the aircraft. This added weight cuts intothe range gains from additional fuel and increases airplane emptyweight.

The airline industry has a need for expanding fuel capacity withoutadding unnecessary weight to the aircraft. Therefore, it would bedesirable to have a method and apparatus that takes into account atleast some of the issues discussed above, as well as other possibleissues.

SUMMARY

An illustrative embodiment of the present disclosure provides a fuelcontainment system. The fuel containment system comprises an upper fuelbarrier, an aft wheel well bulkhead, an aft fuel barrier opposite theaft wheel well bulkhead, a lower fuel barrier associated with a cargofloor, and a lower fuselage skin panel. A fuel tank is created by theupper fuel barrier, the aft wheel well bulkhead, the aft fuel barrier,the lower fuel barrier and the lower fuselage skin panel. The upper fuelbarrier is located below a cabin floor and configured to prevent fuelfrom contacting the cabin floor. The lower fuel barrier is the cargofloor, having been properly sealed to prevent leakage. The lowerfuselage skin panel forms two curved sides of the fuel tank.

Another illustrative embodiment of the present disclosure provides amethod for containing fuel in an aircraft. An upper fuel barrier isinstalled below a cabin floor. An electrical system runs between theupper fuel barrier and the cabin floor. A lower fuel barrier, mostcommonly the cargo floor, is sealed to prevent fuel leaks. An aft wheelwell bulkhead is sealed as well. An aft fuel barrier is installedopposite the aft wheel well bulkhead. Fuel is stored in a fuel tankcreated by the upper fuel barrier, the aft wheel well bulkhead, the aftfuel barrier, the lower fuel barrier, and a lower fuselage skin on thesides. A fuel transport system runs inside the fuel tank.

A further illustrative embodiment of the present disclosure provides afuel containment system having an upper fuel barrier, an aft wheel wellbulkhead, an aft fuel barrier opposite the aft wheel well bulkhead, anda lower fuselage skin panel. The upper fuel barrier is located below acabin floor. The fuel tank is created by the upper fuel barrier, the aftwheel well bulkhead, the aft fuel barrier, and the lower fuselage skinpanel. The fuel tank may remain under cabin pressure. A gas supplysource associated with a number of transport elements supplies a gasinto the fuel tank to replace the fuel pumped out of the fuel tank. Fuelsupply lines are located inside the fuel tank, while electrical systemsare routed through a channel system between the cabin floor and theupper fuel barrier. Support members are located inside the fuel tank aswell.

The features and functions can be achieved independently in variousembodiments of the present disclosure or may be combined in yet otherembodiments in which further details can be seen with reference to thefollowing description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features believed characteristic of the illustrativeembodiments are set forth in the appended claims. The illustrativeembodiments, however, as well as a preferred mode of use, furtherobjectives and features thereof, will best be understood by reference tothe following detailed description of an illustrative embodiment of thepresent disclosure when read in conjunction with the accompanyingdrawings, wherein:

FIG. 1 is an illustration of an aircraft in accordance with anillustrative embodiment;

FIG. 2 is an illustration of a block diagram of an aircraft inaccordance with an illustrative embodiment;

FIG. 3 is an illustration of a perspective view of a fuselage sectionwith an integrated fuel tank in accordance with an illustrativeembodiment;

FIG. 4A is an illustration of a cross-sectional view of a fuselagesection with an auxiliary fuel tank in accordance with the prior art;

FIG. 4B is an illustration of a cross-sectional view of a fuselagesection with an integrated fuel tank in accordance with an illustrativeembodiment;

FIG. 5A is an illustration of a cut plan view of a fuselage section withan auxiliary fuel tank in accordance with the prior art;

FIG. 5B is an illustration of a cut plan view of a fuselage section withan integrated fuel tank in accordance with an illustrative embodiment;

FIG. 6 is an illustration of perspective view of an alternativeimplementation of an integrated fuel tank in accordance with anillustrative embodiment;

FIG. 7 is an illustration of a cross-sectional view of a reinforcedfuselage section with an integrated fuel tank in accordance with anillustrative embodiment;

FIG. 8 is an illustration of a flowchart of a process for containingfuel in an aircraft in accordance with an illustrative embodiment;

FIG. 9 is an illustration of a block diagram of an aircraftmanufacturing and service method in accordance with an illustrativeembodiment; and

FIG. 10 is an illustration of a block diagram of an aircraft in which anillustrative embodiment may be implemented.

DETAILED DESCRIPTION

The illustrative embodiments recognize and take into account one or moredifferent considerations. For example, the illustrative embodimentsrecognize and take into account that it is desirable to improve flightrange by adding fuel capacity to an aircraft. Currently employedsolutions use existing aircraft designs and retrofit auxiliary fueltanks into the cargo bay. Airlines replace cargo with these auxiliaryfuel tanks. While the auxiliary fuel tanks increase fuel capacity, theyreduce usable cargo space. The reduction in cargo space limits revenuefor the airline.

The illustrative embodiments further recognize and take into accountthat it is desirable to keep the aircraft as light as possible. Eachauxiliary fuel tank installed in the cargo bay adds more structure and,in turn, more weight to the aircraft. Support structures and tank wallsmust be added to address crashworthiness concerns. The weight increasemay stunt range gains more than desired.

Therefore, it is desirable to improve aircraft range while minimizingweight increases and providing effective use of cargo space and thus,keeping consistent cargo revenue for the airline. The illustrativeembodiments address these concerns, providing an integrated fuel tankbuilt into the fuselage of the aircraft. Instead of creating a separatetank and adding more weight to the aircraft, the illustrativeembodiments use existing barriers within the cargo bay as tank walls.Supply lines, transport elements, hydraulic systems, and electricallines are rerouted to accommodate this new design.

Thus, the disclosed embodiments provide a fuel containment system havingan upper fuel barrier, an aft wheel well bulkhead, an aft fuel barrieropposite the aft wheel well bulkhead, a lower fuel barrier, and a lowerfuselage skin panel. A fuel tank is created by the upper fuel barrier,the aft wheel well bulkhead, the aft fuel barrier, the lower fuelbarrier, and the lower fuselage skin panel on the sides. This integratedfuel tank has a capacity of approximately twice the volume of currentlyused tanks and adds less than half the weight to the aircraft.

With reference now to the figures and, in particular, with reference toFIG. 1, an illustration of an aircraft is depicted in accordance with anillustrative embodiment. In this illustrative example, aircraft 100 haswing 102 and wing 104 attached to fuselage 106. Aircraft 100 includesengine 108 attached to wing 102 and engine 110 attached to wing 104.

Fuselage 106 has nose section 112, tail section 114, and skin 115.Horizontal stabilizer 116, horizontal stabilizer 118, and verticalstabilizer 120 are attached to tail section 114 of fuselage 106.

In this illustrative example, passenger cabin 122 includes seats 124.Cargo bay 126 includes fuel tank 128.

Turning now to FIG. 2, an illustration of a block diagram of an aircraftis depicted in accordance with an illustrative embodiment. Aircraft 200is an example of one type of platform where fuel containment system 202may be implemented. Fuel containment system 202 uses existing structuralcomponents of aircraft 200 to store fuel 204.

As depicted, fuel containment system 202 is located in cargo bay 206 ofaircraft 200 below cabin floor 208 of passenger cabin 210. Fuelcontainment system 202 comprises upper fuel barrier 212, aft wheel wellbulkhead 214, aft fuel barrier 216, lower fuel barrier 217, and lowerfuselage skin panel 218. Fuel tank 220 is created by upper fuel barrier212, aft wheel well bulkhead 214, aft fuel barrier 216, and lower fuelbarrier 217. Lower fuel barrier 217 may be associated with cargo floor219, integrated in cargo floor 219, or cargo floor 219 may be used aslower fuel barrier 217 after proper seal.

When cargo floor 219 is absent in the area where fuel tank 220 isintegrated, lower fuel barrier 217 may be associated with lower fuselageskin panel 218, integrated in lower fuselage skin panel 218, or lowerfuselage skin panel 218 may be used as lower fuel barrier 217 afterproper seal. Since fuel tank 220 is integrated into cargo bay 206, fueltank 220 may be under cabin pressure 222.

Aft wheel well bulkhead 214 and lower fuselage skin panel 218 arestandard components in aircraft 200. In other words, aft wheel wellbulkhead 214 and lower fuselage skin panel 218 are part of the typicaldesign of aircraft 200. Upper fuel barrier 212 and aft fuel barrier 216must be added to the standard design specifications for aircraft 200.However, these structural additions, as well as the other supports andrelated components may add less than 0.6 lb. per gallon of fuel.

In this illustrative example, upper fuel barrier 212 is a structuralcomponent installed below cabin floor 208. Upper fuel barrier 212 isconfigured to prevent fuel 204 from leaking out of fuel tank 220 andcontacting cabin floor 208 or other components within passenger cabin210. Upper fuel barrier 212 is oriented opposite lower fuel barrier 217and provides the upper boundary for fuel tank 220.

Channel system 224 exists between upper fuel barrier 212 and cabin floor208. Channel system 224 is created by longitudinal beams 225. In thecurrently used design for aircraft 200, beams below passenger cabin 210run in the transverse direction, from one side to another. In anillustrative embodiment, beams are run longitudinally instead, thuscreating a channel between each pair of longitudinal beams 225 such thatvarious transport elements may run through channel system 224.

Electrical system 226 is routed through channel system 224. Electricalsystem 226 may comprise a number of electrical lines that provideelectricity to various parts of aircraft 200. Additional transportelements for electricity, fluid, gas, fiber optics, or other systemsalso may be routed through channel system 224, depending on theparticular implementation.

As used herein, “a number of” when used with reference to items meansone or more items. Thus, a number of electrical lines is one or moreelectrical lines.

Aft wheel well bulkhead 214 is a structural component that provides theforward side wall for fuel tank 220. Aft wheel well bulkhead 214supports the differential pressure between cabin air and ambient air.When fuel tank 220 is under cabin pressure 222, number of transportelements 227 are needed between fuel tank 220 and cargo bay 206. Numberof transport elements 227 are in fluid communication with fuel tank 220.Number of transport elements 227 are configured to supply gas 228 tofuel tank 220 to replace volume 230 of fuel 204 pumped out of fuel tank220.

In this illustrative example, gas 228 may comprise at least one ofnitrogen, other inert gases, or some combination thereof tosubstantially reduce the risk of combustion. Gas supply system 232comprises a number of components configured to supply gas 228 to fueltank 220. Gas supply system 232 may be a compressor, a pump, or someother suitable system. In some illustrative examples, gas supply system232 may include nitrogen gas system (NGS) plumbing.

As used herein, the phrase “at least one of,” when used with a list ofitems, means different combinations of one or more of the listed itemsmay be used, and only one of each item in the list may be needed. Inother words, “at least one of” means any combination of items and numberof items may be used from the list, but not all of the items in the listare required. The item may be a particular object, a thing, or acategory.

For example, “at least one of item A, item B, or item C” may include,without limitation, item A, item A and item B, or item B. This examplealso may include item A, item B, and item C, or item B and item C. Ofcourse, any combination of these items may be present. In otherexamples, “at least one of” may be, for example, without limitation, twoof item A, one of item B, and ten of item C; four of item B and seven ofitem C; or other suitable combinations.

As illustrated, vertical support members 234 are associated with atleast one of aft wheel well bulkhead 214 or aft fuel barrier 216.Vertical support members 234 may be located inside or outside of thefuel barrier. For example, vertical support members 234, when associatedwith aft wheel well bulkhead 214 are located inside fuel tank 220.Vertical support members 234 associated with aft fuel barrier 216 may belocated outside of fuel tank 220. Vertical support members 234 providestructural support for aft wheel well bulkhead 214, aft fuel barrier216, and fuel tank 220. Longitudinal beams 225 connect to verticalsupport members 234.

Aft fuel barrier 216 is a structural component that provides the aftside wall of fuel tank 220. Aft fuel barrier 216 is positioned oppositeaft wheel well bulkhead 214.

The bottom of fuel tank 220 is bound by lower fuel barrier 217. Theother two sides of fuel tank 220 are bound by the curvature of lowerfuselage skin panel 218. No additional structural barriers are used forthe sides of fuel tank 220. Instead, lower fuselage skin panel 218serves as the barrier.

More volume 230 of fuel 204 can be stored in fuel tank 220 in thisillustrative example as compared to currently used fuel tanks becausethe sides of fuel tank 220 are bound by the fuselage skin. In someillustrative examples, no floor exists between lower fuselage skin panel218 and fuel 204 in fuel tank 220. The elimination of a cargo floorallows for even more fuel 204 to be stored.

Aircraft 200 must qualify for crashworthiness to be certified to fly.Crashworthiness certification requires aircraft 200 to land on its bellywithout landing gear and fuel tank 220 must remain intact. Additionalstructure, liners, a bladder, or increased fuselage skin thickness atthe bottom of the aircraft 200 may be needed.

When cargo floor 219 remains present, crash zone 235 is located betweencargo floor 219 and lower fuselage skin panel 218. When cargo floor 219is absent, number of layers of composite material 236 may be bonded tolower fuselage skin panel 218 underneath fuel tank 220. Number of layersof composite material 236 are configured to increase strength 238 oflower fuselage skin panel 218. Number of layers of composite material236 may take the form of doubler plies in this illustrative example. Thedoubler plies may be a separate bonded skin or simply an increased skinthickness of lower fuselage skin panel 218.

Cargo bay 206 of aircraft 200 has number of stanchions 240. Number ofstanchions 240 provide structural support for cabin floor 208. At leastone of number of stanchions 240 has been removed to increase capacity242 of fuel tank 220.

As illustrated, cargo or cargo containers 244 are stored in cargo bay206. Fuel tank 220 has a length of two cargo containers 244 in cargo bay206 in this illustrative example. In other illustrative examples, fueltank 220 may take up the space of more or fewer cargo containers.

Fuel containment system 202 also comprises fuel supply system 246. Fuelsupply system 246 is located inside fuel tank 220. Fuel supply system246 may be configured to transport fuel in and out of fuel tank 220 atdifferent times. These systems may include at least one of plumbing,pumps, sumps, tubing, drains, vents, and other suitable components.

In this illustrative example, fuel supply system 246 is located insidefuel tank 220 to eliminate costly re-routing of the system. In addition,since fuel supply system 246 is within the fuel barrier, space outsidefuel tank 220 is not needed to house such components, thus increasingcapacity 242 of fuel tank 220. Hydraulic system 248 also may be presentand located outside of fuel tank 220.

Upper fuel barrier 212, aft wheel well bulkhead 214, aft fuel barrier216, lower fuel barrier 217, and lower fuselage skin panel 218 aresealed in this illustrative example. Sealing of these componentsprevents fuel 204 from leaking out of fuel tank 220 and damagingcomponents within cargo bay 206 or passenger cabin 210.

In some illustrative examples, fuel containment system 202 may comprisefuel bladder 250. In such a case, fuel tank 220 may not need additionalsealant. Instead, fuel bladder 250 provides a removable, sealed,compressible bladder for containment of fuel 204.

In this illustrative example, fuel bladder 250 also may provideadditional crashworthiness protection. For instance, a tear resistantfuel bladder 250 may satisfy crashworthiness because damage to thestructure upon impact would not breach the fuel barrier.

Fuel containment system 202 may comprise baffles 252 and ventilationsystem 254 in some illustrative examples. Baffles 252 may take the formof baffle plates inside fuel tank 220. Baffles 252 are configured todirect the flow of fuel 204 in fuel tank 220 to reduce sloshing of fuel204 in an undesired manner during operation of aircraft 200. In otherillustrative examples, other mechanisms may be used to address sloshingof fuel 204.

Ventilation system 254 comprises several ducts. A portion of fuel tank220 may be chamfered to allow for ventilation system 254 or otherductwork to run the length of fuel tank 220 outside of fuel tank 220.These ducts may be return air ducts, auxiliary power unit (APU) ducts,environmental ducts, or some other suitable type of ventilation.

In some illustrative examples, other components may be added to fuelcontainment system 202. For example, without limitation, horizontalstringers may be positioned at the bottom of fuel tank 220. Fuel tank220 may have a truss structure. In other illustrative examples, a keelchord extension may be present.

Reinforcement structures may be added at various points around fuelcontainment system 202. Frame pads also may be used. Access doors may beinstalled in one or more areas of fuel containment system 202 or fueltank 220. Additional wiring, switches, and electrical sources may beadded to electrical system 226 in some cases.

To further reduce weight and provide adequate space for fuel tank 220,some components may be removed from the traditional design of aircraft200. For example, without limitation, liners, insulation, or othercomponents may be removed.

Thus, with an illustrative embodiment, and by integrating fuel tank 220into the fuselage of aircraft 200, capacity 242 of fuel tank 220 issubstantially increased while adding as little additional structure aspossible. The fuselage has many panels that are already designed to holdpressure. These panels are utilized as fuel barriers rather than addingmore panels.

The impact on cargo space is the same or reduced over currently usedauxiliary fuel tank solutions. For example, with the use of anillustrative embodiment, aircraft 200 can keep 21 inches of cargo space.Since fuel tank 220 expands farther to the sides in cargo bay 206, morevolume is realized with less length. As a result, the integrated fueltank 220 increases revenue ability from cargo while also increasing therange of aircraft 200

An illustrative embodiment can also be used in conjunction withremovable auxiliary tanks. For instance, fuel tank 220 may be integratedinto cargo bay 206 while an auxiliary tank may be placed in cargo bay206 in another portion of aircraft 200, depending on the needs of theflight.

With reference next to FIG. 3, an illustration of a perspective view ofa fuselage section with an integrated fuel tank is depicted inaccordance with an illustrative embodiment. A perspective view ofaircraft 100 from FIG. 1 is shown with a portion of the skin of fuselage106 removed. FIG. 3 illustrates an example of physical implementationsfor components within aircraft 200 as shown in block form in FIG. 2. Theforward portion of the aircraft is indicated by an arrow.

As depicted, fuel tank 128 in FIG. 1 takes the form of integrated fueltank 300. Integrated fuel tank 300 and the components described hereinare part of fuel containment system 301 in this illustrative example.

Integrated fuel tank 300 comprises aft wheel well bulkhead 302, aft fuelbarrier 304, upper fuel barrier 306, and lower fuel barrier 308. Lowerfuel barrier 308 takes the form of cargo floor 310 in this illustrativeexample. Upper fuel barrier 306 is shown in phantom in this view.Integrated fuel tank 300 has chamfered edge 312 and chamfered edge 314.Crash zone 316 is present between cargo floor 310 and lower fuselageskin 309. Length 318 of integrated fuel tank 300 is approximately thesame length as two cargo containers (not shown in this view).

In this illustrative example, fuel supply system 320 is insideintegrated fuel tank 300. Integrated fuel tank 300 is shown withoutfuel.

Vertical support members 322, vertical support members 324, andlongitudinal beams 325 are shown. Vertical support members 322 are onthe aft side of aft fuel barrier 304, while vertical support members 324are located inside integrated fuel tank 300.

FIG. 4A and FIG. 4B are comparative cross-sectional views of the priorart and the integrated fuel tank as described herein, taken along lines4-4 in FIG. 1. FIG. 4A is an illustration of a cross-sectional view of afuselage section with an auxiliary fuel tank in accordance with theprior art, while FIG. 4B is an illustration of a cross-sectional view ofa fuselage section with an integrated fuel tank in accordance with anillustrative embodiment.

FIG. 4A shows fuselage 106 with skin 115 and frames 400 around theinside of the fuselage 106 and running lateral to the fuselage length.Cabin floor 402 spans fuselage 106 and supports seats 124 and passengerwalking traffic in passenger cabin 122.

As illustrated, cargo floor 310 spans a lower section of fuselage 106and supports loose cargo and cargo containers in cargo bay 126.Stanchions 408 support the main deck floor by attaching to frames 400 inthe cargo bay 126. To increase range of aircraft 100, auxiliary fueltank 410 is added to cargo bay 126 in place of a cargo container.Auxiliary fuel tank 410 can be filled with fuel 412 to increase therange of aircraft 100. Capacity of fuel 412 in auxiliary fuel tank 410is approximately 790 gallons.

In this illustrative example, cargo bay 126 has dead space 414, deadspace 416, dead space 418, and dead space 420 around auxiliary fuel tank410. These spaces may be used to route fuel supply lines, ventilation,hydraulic components, or electrical systems. However, such spacerestricts the fuel capacity of auxiliary fuel tank 410. Horizontal beam421 is shown above auxiliary fuel tank 410 connecting to stanchions 408on either side of auxiliary fuel tank 410.

FIG. 4B shows fuselage 106 with skin 115 and frames 400 supporting skin115. Cabin floor 402 separates the passenger cabin 122 from cargo bay126, below.

Fuel containment system 429 comprises integrated fuel tank 430 boundedby cargo floor 310 on bottom, by lower fuselage skin panel 431 on thesides, and by upper fuel barrier 432 on top. Upper fuel barrier 432prevents fuel 412 from wetting cabin floor 402 and electrical systems434.

Electrical systems 434 run outside upper fuel barrier 432. Fuel systems436 runs through integrated fuel tank 430. Frames 400 are in integratedfuel tank 430 and increases the fuel capacity by the volume of spacebetween frames 400 to the height of frames 400. Stanchions 408 may beremoved to increase fuel volume in integrated fuel tank 430 orstanchions 408 may remain. If stanchions 408 remain, stanchions 408 aresealed at upper fuel barrier 432 and cargo floor 310. Fuel capacity goesall the way to the sides of the cargo bay skin in this illustrativeexample. Longitudinal support beams 438 run under cabin floor 402.

As illustrated, upper fuel barrier 432 has chamfered edge 440 andchamfered edge 442. Lower fuselage skin panel 431, chamfered edge 440 ofupper fuel barrier 432, and cabin floor 402 connect to form channel 444.In a similar fashion, lower fuselage skin panel 431, chamfered edge 442of upper fuel barrier 432, and cabin floor 402 connect to form channel446. Electrical systems 434 run through channels created between pairsof longitudinal support beams 438, while ventilation system 448 runsthrough channel 446 and channel 444.

FIG. 5A and FIG. 5B are comparative cut plan views of aircraft 100 withthe prior art and the integrated fuel tank as described herein. FIG. 5Ais an illustration of a cut plan view of a fuselage section with anauxiliary fuel tank in accordance with the prior art, while FIG. 5B isan illustration of a cut plan view of a fuselage section with anintegrated fuel tank in accordance with an illustrative embodiment.

FIG. 5A shows a top down view of a fuselage 106 where forward is to theleft and aft to the right. Auxiliary fuel tank 410 is sitting forward inaft cargo hold adjacent to aft wheel well bulkhead 422. Wheel well 424is a cut out in fuselage 106 where landing gear 426 is stored. Aft wheelwell bulkhead 422 must withstand fuselage pressure and is supported bysupport members 428 to prevent the planar bulkhead from deforming.

FIG. 5B shows the plan view of fuselage 106 cut away under cabin floor402. Fuel 412 is bounded on four sides in this figure. The outboardsides are bounded by lower fuselage skin panel 431 with frames 400inside the fuel barrier. The forward side of the tank is bounded by aftwheel well bulkhead 422 with support members 428 inside the fuelbarrier. The aft side of integrated fuel tank 430 is bounded by aft fuelbarrier 450. Aft wheel well bulkhead 422 supports the differentialpressure so when integrated fuel tank 430 is under cabin pressure, afluid communication means may be required between integrated fuel tank430 and cargo bay 126.

Turning next to FIG. 6, an illustration of a perspective view of analternative implementation of an integrated fuel tank is depicted inaccordance with an illustrative embodiment. FIG. 6 shows an alternativeimplementation for fuel tank 220 and the components within fuel tank 220from FIG. 2.

Integrated fuel tank 600 comprises aft wheel well bulkhead 302, aft fuelbarrier 304, upper fuel barrier 306, and lower fuselage skin 309. Cargofloor 310 has been removed in this view, thus no crash zone 316 ispresent.

In FIG. 7, an illustration of a cross-sectional view of a reinforcedfuselage section with an integrated fuel tank is depicted in accordancewith an illustrative embodiment. Aircraft 100 must qualify forcrashworthiness to be certified to fly. Qualification may requireadditional structure or increased skin thickness or a bladder/liner atthe bottom of the airplane. This illustrative example shows the belly offuselage 106 with doubler plies 700 and support structures 702.

The different components shown in FIG. 1 and FIGS. 3-7 may be combinedwith components in FIG. 2, used with components in FIG. 2, or acombination of the two. Additionally, some of the components in FIG. 1and FIGS. 3-7 may be illustrative examples of how components shown inblock form in FIG. 2 may be implemented as physical structures. Otherconfigurations for a fuel containment system 429 may be implementedother than those shown in FIGS. 3-8.

Although the illustrative embodiments are described with reference toaircraft, the illustrative embodiments may have application to othertypes of platforms. For example, without limitation, an integrated fueltank as described herein may be implemented in a mobile platform, astationary platform, a land-based structure, an aquatic-based structure,or a space-based structure. More specifically, an integrated fuel tankmay be used in a rotorcraft, a surface ship, a tank, a personnelcarrier, a train, a spacecraft, a space station, a satellite, asubmarine, an automobile, a power plant, a bridge, a dam, a house, amanufacturing facility, a building, and other suitable platforms.

The terms “lower fuselage skin” and “lower fuselage skin panel” may beused interchangeably. One or more fuselage skin panels may be used toform two of the sides of the integrated fuel tank.

With reference next to FIG. 8, an illustration of a flowchart of aprocess for containing fuel in a fuel tank is depicted in accordancewith an illustrative embodiment. The method depicted in FIG. 8 may beused with fuel containment system 202 in FIG. 2 to improve fuel capacityin aircraft 200 while minimizing weight increases.

The process begins by sealing a lower fuel barrier associated with acargo floor (operation 800). Next, an upper fuel barrier is installedbelow a cabin floor (operation 802).

The aft wheel well bulkhead is sealed (operation 804). The process theninstalls an aft fuel barrier in a cargo bay (operation 806). Fuel ispumped into a fuel tank created by the upper fuel barrier, the aft wheelwell bulkhead, the aft fuel barrier, and the lower fuel barrier(operation 808).

As the aircraft is in operation, fuel is transported out of the fueltank to a central tank (operation 810). A gas is supplied to the fueltank to replace a volume of fuel pumped out of the fuel tank until thefuel tank is empty (operation 812), with the process terminatingthereafter.

Illustrative embodiments of the disclosure may be described in thecontext of aircraft manufacturing and service method 900 as shown inFIG. 9 and aircraft 1000 as shown in FIG. 10. Turning first to FIG. 9,an illustration of a block diagram of an aircraft manufacturing andservice method is depicted in accordance with an illustrativeembodiment. During pre-production, aircraft manufacturing and servicemethod 900 may include specification and design 902 of aircraft 1000 inFIG. 10 and material procurement 904.

During production, component and subassembly manufacturing 906 andsystem integration 908 of aircraft 1000 in FIG. 10 takes place.Thereafter, aircraft 1000 in FIG. 10 may go through certification anddelivery 910 in order to be placed in service 912. While in service 912by a customer, aircraft 1000 in FIG. 10 is scheduled for routinemaintenance and service 914, which may include modification,reconfiguration, refurbishment, and other maintenance or service.

Fuel containment system 202 from FIG. 2 may be made during component andsubassembly manufacturing 906. In addition, components within fuelcontainment system 202 may be implemented during routine maintenance andservice 914 as part of a modification, reconfiguration, or refurbishmentof aircraft 1000 in FIG. 10.

Each of the processes of aircraft manufacturing and service method 900may be performed or carried out by a system integrator, a third party,an operator, or some combination thereof. In these examples, theoperator may be a customer. For the purposes of this description, asystem integrator may include, without limitation, any number ofaircraft manufacturers and major-system subcontractors; a third partymay include, without limitation, any number of vendors, subcontractors,and suppliers, and an operator may be an airline, a leasing company, amilitary entity, a service organization, and so on.

With reference now to FIG. 10, an illustration of a block diagram of anaircraft is depicted in which a composite structure made using anillustrative embodiment may be implemented. In this example, aircraft1000 is produced by aircraft manufacturing and service method 900 inFIG. 9 and may include airframe 1002 with plurality of systems 1004 andinterior 1006. Examples of systems 1004 include one or more ofpropulsion system 1008, electrical system 1010, hydraulic system 1012,and environmental system 1014. Any number of other systems may beincluded. Although an aerospace example is shown, different illustrativeembodiments may be applied to other industries, such as the automotiveindustry.

Apparatuses and methods embodied herein may be employed during at leastone of the stages of aircraft manufacturing and service method 900 inFIG. 9. In one illustrative example, components or subassembliesproduced in component and subassembly manufacturing 906 in FIG. 9 may befabricated or manufactured in a manner similar to components orsubassemblies produced while aircraft 1000 is in service 912 in FIG. 9.As yet another example, one or more apparatus embodiments, methodembodiments, or a combination thereof may be utilized during productionstages, such as component and subassembly manufacturing 906 and systemintegration 908 in FIG. 9. One or more apparatus embodiments, methodembodiments, or a combination thereof may be utilized while aircraft1000 is in service 912, during maintenance and service 914 in FIG. 9, orboth. The use of a number of the different illustrative embodiments maysubstantially expedite the assembly of aircraft 1000, reduce the cost ofaircraft 1000, or both expedite the assembly of aircraft 1000 and reducethe cost of aircraft 1000.

With the use of an illustrative embodiment, the needs identified in theaerospace field can be alleviated by a fuel tank that is permanent andlight weight because it uses the fuselage skin as the fuel barrier. Theairplane will have more fuel volume with little to no additionalstructure.

An illustrative embodiment may be implemented to meet crashworthinessindex scores in aircraft, as well as other applications. The apparatusesand methods disclosed herein reduce weight while providing more rangefor the aircraft as less cost to cargo space than currently usedauxiliary fuel tanks.

In some alternative implementations of an illustrative embodiment, thefunction or functions noted in the blocks may occur out of the ordernoted in the figures. For example, in some cases, two blocks shown insuccession may be executed substantially concurrently, or the blocks maysometimes be performed in the reverse order, depending upon thefunctionality involved. Also, other blocks may be added, in addition tothe illustrated blocks, in a flowchart or block diagram.

The description of the different illustrative embodiments has beenpresented for purposes of illustration and description, and is notintended to be exhaustive or limited to the embodiments in the formdisclosed. Many modifications and variations will be apparent to thoseof ordinary skill in the art. Further, different illustrativeembodiments may provide different features as compared to otherdesirable embodiments. The embodiment or embodiments selected are chosenand described in order to best explain the principles of theembodiments, the practical application, and to enable others of ordinaryskill in the art to understand the disclosure for various embodimentswith various modifications as are suited to the particular usecontemplated.

What is claimed is:
 1. A fuel containment system comprising: an upperfuel barrier located below a cabin floor and configured to prevent fuelfrom contacting the cabin floor; an aft wheel well bulkhead; an aft fuelbarrier opposite the aft wheel well bulkhead; a lower fuel barrierassociated with a cargo floor; and a lower fuselage skin panel.
 2. Thefuel containment system of claim 1 further comprising: a fuel tankcreated by the upper fuel barrier, the aft wheel well bulkhead, the aftfuel barrier, the lower fuel barrier, and the lower fuselage skin panel.3. The fuel containment system of claim 2 further comprising: a fuelsupply system inside the fuel tank, wherein the fuel supply system isconfigured to transport the fuel out of the fuel tank.
 4. The fuelcontainment system of claim 2, wherein the fuel tank is integrated intoa cargo bay, and wherein the fuel tank is under cabin pressure.
 5. Thefuel containment system of claim 2, wherein at least one stanchion wasremoved to increase a capacity of the fuel tank.
 6. The fuel containmentsystem of claim 2 further comprising: support members inside the fueltank and associated with the aft wheel well bulkhead.
 7. The fuelcontainment system of claim 2 further comprising: a number of transportelements in fluid communication with the fuel tank and configured tosupply a gas to the fuel tank to replace a volume of the fuel pumped outof the fuel tank.
 8. The fuel containment system of claim 2 furthercomprising: a fuel bladder inside the fuel tank.
 9. The fuel containmentsystem of claim 2 further comprising: longitudinal beams under the cabinfloor and running a length of the fuel tank from the aft wheel wellbulkhead to the aft fuel barrier; and a channel system between the upperfuel barrier and the cabin floor created by space between a pair oflongitudinal beams, wherein an electrical system is routed through thechannel system.
 10. A method for containing fuel in an aircraft, themethod comprising: sealing a cargo floor to create a lower fuel barrier;installing an upper fuel barrier below a cabin floor; sealing an aftwheel well bulkhead; installing an aft fuel barrier in a cargo bay; andstoring the fuel in a fuel tank created by the upper fuel barrier, theaft wheel well bulkhead, the aft fuel barrier opposite the aft wheelwell bulkhead, and a lower fuselage skin panel.
 11. The method of claim10 further comprising: transporting the fuel out of the fuel tank usinga fuel supply system located inside the fuel tank.
 12. The method ofclaim 10 further comprising: supplying a gas to the fuel tank to replacea volume of the fuel pumped out of the fuel tank.
 13. The method ofclaim 10 further comprising: bonding a number of layers of compositematerial to the lower fuselage skin panel underneath the fuel tank toincrease a strength of the lower fuselage skin panel.
 14. The method ofclaim 10 further comprising: removing a number of stanchions to increasea capacity of the fuel tank; and installing longitudinal beams under thecabin floor and running a length of the fuel tank from the aft wheelwell bulkhead to the aft fuel barrier.
 15. The method of claim 10further comprising: sealing the lower fuselage skin panel from the cargofloor to the upper fuel barrier within the fuel tank.
 16. A fuelcontainment system comprising: an upper fuel barrier below a cabinfloor; an aft wheel well bulkhead; an aft fuel barrier opposite the aftwheel well bulkhead; and a lower fuselage skin panel.
 17. The fuelcontainment system of claim 16 further comprising: a fuel tank formedfrom the upper fuel barrier, the aft wheel well bulkhead, the aft fuelbarrier, and the lower fuselage skin panel; and a fuel bladder insidethe fuel tank.
 18. The fuel containment system of claim 17, furthercomprising: a fuel supply system inside the fuel tank.
 19. The fuelcontainment system of claim 17 further comprising: a number of layers ofcomposite material bonded to the lower fuselage skin panel, wherein thenumber of layers of composite material is configured to increase astrength of the lower fuselage skin panel.
 20. The fuel containmentsystem of claim 17 further comprising: a number of transport elements influid communication with the fuel tank; and a gas supply sourceassociated with the number of transport elements.